The present invention relates to a control equipment to control an actuator based on external states transmitted from sensors through a network, and more particularly to a control equipment with a communication apparatus between microcomputers built into the control equipment and peripheral ICs.
An automotive engine control equipment controls an amount of fuel supply and fuel injection timings according to input signals such as a crank angle sensor signal. The engine control, as it becomes more sophisticated in function, is required to be performed using a growing number of pieces of information, which means that the number of input/output signals is increasing. An engine control equipment with built-in microcomputers is provided with a limited number of input/output signals because of cost limitations. Therefore if the number of input/output signals required to be handled is greater than that of the microcomputer itself, it is common practice in recent years to control the output by the microcomputer communicating with peripheral ICs. Further, associated laws and regulations in recent years require that the control equipment be provided with a diagnostic function. So, the control equipment has come to communicate with these ICs, that have their own diagnostic functions, to obtain diagnostic information. With the above configuration of the control equipment, the likelihood of the communication processing influencing software load has increased. JP-A-6-261099 discloses a configuration that aims to reduce the load of the communication processing by switching between a mode requiring a communication interrupt and a mode not requiring it. As to a communication protocol, some control equipments use SPI (Serial Peripheral Interface) protocol (U.S. Pat. No. 6,880,530 B2 and U.S. Pat. No. 6,684,862 B2). The SPI communication is a master-slave type serial communication protocol characterized in that master and slave data are exchanged in synchronism with clock.
The control equipment described in JP-A-6-261099 normally operates in a mode not requiring the communication interrupt and, during a large-volume data communication, switches to a mode requiring the communication interrupt. At the end of the communication the control equipment returns to the mode not requiring the communication interrupt. This configuration has a drawback that, when the communication in a mode requiring the interrupt occurs in succession, unnecessary switching takes place. Further, in communicating with a plurality of destinations, the control equipment produces an interrupt to execute reception processing before establishing communication with a different destination. This requires an interrupt to be produced each time the communication destination is changed.